Plaquenil, or hydroxychloroquine, and its related compound chloroquine, has long been identified to be associated with a retinal toxicity. This toxicity occurs rarely (in the range of 0.5-3.5% of patients on the drug), but, nevertheless, it remains a concern as the toxicity to the retina is mostly, if not wholly, irreversible and the visual sequelae from this toxicity can be devastating. A relationship has been proposed between mutations in the ABCA4 gene and the development of Plaquenil toxicity. If a relationship between ABCA4 mutations, or other genetic mutations, and Plaquenil toxicity is identified this would enable the practice of personalized medicine. The practice of personalized medicine is supported by a bill from the US congress and utilizes the knowledge gained by genetic sequencing to tailor an individuals medical care. It would follow that patients considered for hydroxychloroquine or chloroquine therapy undergo genetic screening for genetic mutations, such as ABCA4 mutations, so that patients who would be exquisitely sensitive to toxic effects of this drug are identified before the treatment is implemented. The objective of this study is to identify genetic mutations, starting with an analysis of ABCA4 mutations, that may be correlated with Plaquenil toxicity and correlate these with the participants phenotypes. This study has recruited nearly 50 patients with Plaquenil-induced retinal toxicity and at least 50 control participants to participate in this study. This is an observational study that requires 1-2 outpatient visits to the NIH Clinical Center or a local ophthalmologists office over a period of time convenient to the participants, not to exceed two years. After gathering a complete medical, family and surgical history, participants will have standard physical and eye examination. The eye examination will include a dilated fundus examination. Non-invasive ophthalmologic testing (e.g., visual field testing, OCT, photos, and autofluorescence) may be performed. Photographs (ophthalmic) will be taken to document the Plaquenil toxicity. Participants will have a 30 cc blood sample drawn for genetic analysis. We have enrolled participants and continue to enroll participants into this study at the NEI. We have analyzed and published on clinical findings that differ between affected and unaffected groups. We are starting to analyze genetic data.